Mechanochemical processing of polytetrafluoroethylene with NaCl crystals

Abstract

Polytetrafluoroethylene (PTFE) is an indispensable material for society and industry. PTFE chains have a strong intermolecular force and form strongly bound crystal structures. The strong assembly causes a low surface energy and refractive index, as well as difficulty in processing and recycling. In this paper, we describe how PTFE powders were milled with NaCl crystals using a planetary ball mill. Furthermore, the milled PTFE-NaCl powders were immersed in water to remove NaCl, and filtered powders were obtained. These powders were characterized by X-ray diffraction (XRD) and infrared spectroscopy. The PTFE-NaCl powders had a lower XRD peak intensity than that of processed PTFE powders without NaCl. Even the filtered powders had a lower XRD peak intensity. These results suggest that the intermolecular assembly was loosened by the mechanochemical process with NaCl. Then, PTFE-NaCl and filtered powders were pressed to form pellets. The pellets were successfully sintered, while PTFE powders milled without NaCl were not.